Jointed hands offer more posing flexibility, but regular hands usually look more aesthetically pleasing and realistic.
Personally, I prefer regular hands. Jointed ones are often expensive—sometimes the price of one pair can get you three pairs of regular hands. They’re okay for male dolls, but for female dolls, elegant hand shapes often look better.
Also, jointed hands require manual posing for each finger joint, which can be tedious.
In the end, both types have pros and cons. Choose based on what suits your needs best.